Self-Assembly in Silane/Hydrogen Plasmas: from Silicon Atoms to Aromatic Silicon Nanocrystals

We theoretically predict that low pressure silane/hydrogen plasmas may present the ideal venue for the fabrication of a new nanostructured silicon material with strong aromatic properties. Precisely controlling the ratio of atomic and molecular hydrogen concentrations during the growth of hydrogenated silicon clusters in a pulsed plasma enhanced chemical vapor deposition reactor will allow us to “steer” the growth toward over-coordinated silicon nanocrystals that reveal aromatic properties as strong as those of benzene. In addition, those pure silicon nanocrystals demonstrate optical, electrical, and mechanical characteristics that could so far only be obtained by adding toxic or expensive elements (as PbS, PbSe, CdS, CdSe, or Au) in the cluster structure. Due to their light absorption not only in the ultraviolet, but also in the visible and the infrared spectrum, they might, for instance, play a major role for photovoltaic devices or in the hyperthermal treatment of cancer.